package com.clark.io;

import static com.clark.func.Functions.sizeOfDirectory;

import java.io.File;
import java.io.Serializable;
import java.util.Comparator;

/**
 * Compare the <b>length/size</b> of two files for order (see
 * {@link File#length()} and {@link FileUtils#sizeOfDirectory(File)}).
 * <p>
 * This comparator can be used to sort lists or arrays of files by their
 * length/size.
 * <p>
 * Example of sorting a list of files using the {@link #SIZE_COMPARATOR}
 * singleton instance:
 * 
 * <pre>
 *       List&lt;File&gt; list = ...
 *       SizeFileComparator.SIZE_COMPARATOR.sort(list);
 * </pre>
 * <p>
 * Example of doing a <i>reverse</i> sort of an array of files using the
 * {@link #SIZE_REVERSE} singleton instance:
 * 
 * <pre>
 *       File[] array = ...
 *       SizeFileComparator.SIZE_REVERSE.sort(array);
 * </pre>
 * <p>
 * <strong>N.B.</strong> Directories are treated as <b>zero size</b> unless
 * <code>sumDirectoryContents</code> is <code>true</code>.
 * 
 * @version $Revision: 723942 $ $Date: 2008-12-06 01:24:06 +0000 (Sat, 06 Dec
 *          2008) $
 * @since Commons IO 1.4
 */
public class SizeFileComparator extends AbstractFileComparator implements
        Serializable {

    private static final long serialVersionUID = -1545959023382665552L;

    /** Size comparator instance - directories are treated as zero size */
    public static final Comparator<File> SIZE_COMPARATOR = new SizeFileComparator();

    /** Reverse size comparator instance - directories are treated as zero size */
    public static final Comparator<File> SIZE_REVERSE = new ReverseComparator(
            SIZE_COMPARATOR);

    /**
     * Size comparator instance which sums the size of a directory's contents
     * using {@link FileUtils#sizeOfDirectory(File)}
     */
    public static final Comparator<File> SIZE_SUMDIR_COMPARATOR = new SizeFileComparator(
            true);

    /**
     * Reverse size comparator instance which sums the size of a directory's
     * contents using {@link FileUtils#sizeOfDirectory(File)}
     */
    public static final Comparator<File> SIZE_SUMDIR_REVERSE = new ReverseComparator(
            SIZE_SUMDIR_COMPARATOR);

    /** Whether the sum of the directory's contents should be calculated. */
    private final boolean sumDirectoryContents;

    /**
     * Construct a file size comparator instance (directories treated as zero
     * size).
     */
    public SizeFileComparator() {
        this.sumDirectoryContents = false;
    }

    /**
     * Construct a file size comparator instance specifying whether the size of
     * the directory contents should be aggregated.
     * <p>
     * If the <code>sumDirectoryContents</code> is <code>true</code> The size of
     * directories is calculated using {@link FileUtils#sizeOfDirectory(File)}.
     * 
     * @param sumDirectoryContents
     *            <code>true</code> if the sum of the directoryies contents
     *            should be calculated, otherwise <code>false</code> if
     *            directories should be treated as size zero (see
     *            {@link FileUtils#sizeOfDirectory(File)}).
     */
    public SizeFileComparator(boolean sumDirectoryContents) {
        this.sumDirectoryContents = sumDirectoryContents;
    }

    /**
     * Compare the length of two files.
     * 
     * @param file1
     *            The first file to compare
     * @param file2
     *            The second file to compare
     * @return a negative value if the first file's length is less than the
     *         second, zero if the lengths are the same and a positive value if
     *         the first files length is greater than the second file.
     * 
     */
    public int compare(File file1, File file2) {
        long size1 = 0;
        if (file1.isDirectory()) {
            size1 = sumDirectoryContents && file1.exists() ? sizeOfDirectory(file1)
                    : 0;
        } else {
            size1 = file1.length();
        }
        long size2 = 0;
        if (file2.isDirectory()) {
            size2 = sumDirectoryContents && file2.exists() ? sizeOfDirectory(file2)
                    : 0;
        } else {
            size2 = file2.length();
        }
        long result = size1 - size2;
        if (result < 0) {
            return -1;
        } else if (result > 0) {
            return 1;
        } else {
            return 0;
        }
    }

    /**
     * String representation of this file comparator.
     * 
     * @return String representation of this file comparator
     */
    @Override
    public String toString() {
        return super.toString() + "[sumDirectoryContents="
                + sumDirectoryContents + "]";
    }
}
